Railway brake



Feb. 22,

' W. HILDEBRAND RAILWAY BRAKE Filed Feb. 10, 1926' L am WILHELM nrnnnnnnnn, or monrnnrnnnn, BERLIN, GERMANY.

v RAILW'AY BRAKE.

Application filed February 10, 1925,.Se1ia1 No. 87,338, and in Germany February 13, 1925.

This invention relates to fluid pressure brake apparatus for railway vehicles of the kind provided with a brake accelerator and. a transmission chamber to receive air displaced by the piston of the controlling valve. The invention is, intended for use with pneumatic or air pressure brakes.

In known 7 arrangements of pneumatic brakes wherein a braking action begins upon a fall in pressure in the train pipe, and

V in order to prevent the air displaced by the pistonof the controlling-valve from being delivered into the train pipe and there accumulatingto an extent depending on the number of controlling valves present in the train, a quantity of air'co-rresponding with the'displacement volume of the controlling piston is guided by the brake accelerator into a transmission chamber, the "difficulty e'z iiststhat the accelerator does not open the entrance to the transmission chamber until the. controlling piston has already forced some air into the train pipe, and consequently an excessive reduction-in pressure in the train pipe is necessary'to ensure the braking action, especially towards the end of a long train.

According to this invention this difficulty is. overcome by arranging the transmission chamber to be connected by a. brake accelerator having. a piston of short stroke with the train pipe before the movement of the controlling piston begins.

In order that the said invention may be clearly understood and readily carried into elfect, the same will bemore fully described with reference to the accompanying diagram, wherein Figure 1 represents in section one constructional embodiment of the invention. e 7

Figure 2 represents in section another constructional embodiment.

Figure 3 represents an accelerator with a flap valve instead of a slide valve.

Lrindicates a pipe communicating with thetrain pi e, S the casing of the controlling valve, the casing of theaccelerator,

U the transmission chamber, ILtllG auxiliary air reservoir, and C the duct leading to the brake cylinder.v The controlling valve consists: of the casing S, the controlling piston 76 contained therein and the stepped slide 8 rigidly connected therewith, the said slide 3 being adapted to slide with play or clearance upon the main slide 9. The

controlling piston rod is prolonged beyond the steppe Slide 8 andcarries ,atits end a small piston 0 which acts as a closing valve for a connecting pipe between I the brake accelerator casing B and the controlcounter piston in relation to the. controlling '60 1mg valve casing ,S- and also acts as a piston 76, the air pressure on the inner surface of the piston is being counteracted to mission chamber and the valve 79 controls the connection between the pipe 0 and the outlet 2' to the atmosphere and also that between the pipe reservoir H.

The auxiliary air reservoir is brake accelerator casing. The outlet ofthe air from the transmission chamber U is con trolled by the main slide 9, for this purpose th transmission chamber is in communication with the port of the slide throughthe pipe f.

l Vhen allowed to escape from the pipe L by operating the drivers valve, the piston g of the brake accelerator B which ijsrunder pressure from the reservoir Hwill atonce approach 1 the pipe L, as the slide valves a and Z2 moved by it can be made very small, and the faces of these slide valves covering the apertures can be of such small dimensions that the resistances opposing the movement of the piston q are also very small, so that said chamber, avoiding interference with the dropin pressure inthe train pipe the small volume of airdisplaced ,by the accelerator piston g. .The controlling piston is, on the contrary, does not move at once out of the release position upon the inception of the braking action, because it is held back by resistance of the counter piston o,

The valve 60 thus controls the connecfor the purpose of initiating the brake action a small quantity of air is,

7 5. 0 and the auxiliary air connectedi by the pipe cl with the controlling slide valve chamber, and by the pipe ew'ith the but when the pressure in the pipe L has fallen to a certain extent, the pressure of air from the auxiliary reservoir H upon the back or the larger piston k overcomes the pressure on the smaller piston 42 and enables the piston is to advance and open the duct C leading to the brake cylinder. In order to prevent the loss of air from the transmission chamber, as long as the slide 9 has not'shut oil the ole-aerating pipe f from the open air outlet m, a contraction h is provided in the said pipe f which only permits of a very gradual escape of the air from the chamber U. In order to prevent the retardation of the controlling piston is, in relation tothe brake accelerator piston from becoming greater than is necessary for filling the chamber U, the casing of the brake accelerator is connected with the controlling valve casing by means of a pipe 0 which, when a braking operation takes place, allows air from the auxiliary reservoir to pass below the counter piston 0;,so that this small counter piston is soon subjected on both sides to equal pressure conditions and thus loses relatively to the valve g, to which it trans- I I mits impulses received from thero'd 70 of with the said duct m.

the piston 70, this action however being cletterred so thatthe movement in each direction of the valve 9 only begins after the valve 8 has accomplished a part of its stroke. In the position illustrated in the drawings, that is, the release position, the

duct f communicates with the duct at through a hollow in the valve g, and the duct C also communicates through a hollow in the valve 8 and through the valve 9 When owing to a reduction of pressure in the train pipe the piston kadvances, the valve 8 first shuts ofi the supply pipe C leading to the brake cylinder from the atmosphere relief duct m,

then moves the valve 9 to shut off the duct m from the pipe f and on the further movement of the valve g of the pipe C is opened to theair pressure from the auxiliary reservoir H. acting through the interior of the casing S of the control valve. I

' The same effect canalso berealized without employing a retarding piston 0 when the resistances, which are eiiective against the movement of the accelerator piston, are substantially smaller than the movement resistances of the controlling piston is with the slides gand 8 This is the case when the controlling member a, to be moved by the accelerator piston, is made as sn'iall as possible, that is to say when this member has only to control one single connection,

namely that between the pipe L and the transmission chamber. Figures 2 and 3 show constructional forms of this type.

In the constructional form according to Figure 2 the connection between the pipe L and the transmission chamber is controlled by the very small slide valve'ct. Both the slide valve friction and the slide valve path are unusually small in the constructional form. r

In the constructional form according to Figure 3 a small easily movable flap valve serves to control the said connection.

.What I claim and desire to secure by Letters Patentot the United States is 1. In a pneumatic brake, a'train pipe, an auxiliary air reservoir, a control valve comprising a piston to control the connection of said reservoir with the brake cylinder, an

accelerator comprising a piston of shorter stroke and less frictional resistance to movement than said control valve piston, said acceleratorpiston being enposed'to air pressure from said auxiliary reservoir, a transj fer chamber, a valve controlling admission of air from said train pipe to said transfer chamber, and means 'operatively connected with said accelerator piston to open and close the last named va ve 2. In a brake according to claim 1, a piston actuating the controlling valve, said pis ton being provided with a loading device to retard the commencement of its movement 3. In a brake according to claim 1, a pis:

ton actuating the controlling valve, said piston being provided with a loading device to retard the commencement'ot its movement, and means whereby the retarding etfeet of said loading device'is suspended by 'the action of the accelerator upon inception of a braking operation,

4. In a brake according to claim 1, means whereby the connection of the transmission chamber with the open air is effected by the action of the, controlling valve.

5. In a brake according to claim 1,

auxiliary air reservoir adapted to, constitute the controlling container to actuate the piston of the brake cylinder.v

VVILHELM I'IILDEBRAND. 

